Operating systems

Cyphesis is a server for MMORPG games. It is the core engine of the WorldForge project and is currently focused on implementing fantasy games, providing rich scripting, full world persistence, and basic physics.

Deliantra is an advancement of the crossfire
multi-user RPG game. Unlike the original project,
it focuses mainly on stability and playability,
but also adds modern technology such as map
scripting, Perl server extensions, asynchronous
I/O, higher resolution graphics, and better client
support.

Ryzom Core is a toolkit for the development of massively online universes. It was used to make the commercial MMORPG Ryzom. It provides the base technologies and a set of development methodologies for the development of both client and server code.

RainbruRPG is a 3D multiplayer Role Playing Game project based on Ogre3D and CEGUI. It is based on an Object Oriented design through C++ and Ruby modules and a community-oriented concept through a wiki.